PROFINET®,EtherNet/IP, and Ethernet Connectivity Solutions - Belden

Industrial Ethernet Media
Cordsets, Connectors
and Switches with Plug-
N-Play Features Reduce
Overall Installation and
Maintenance Costs.
6
Introduction to PROFINET, EtherNet/IP and Ethernet
About Industrial Ethernet
The use of Ethernet in IT for connecting various
terminals is widespread, especially in local area
networks (LAN). Since 1985, the Institute of
Electrical and Electronics Engineers (IEEE) has
used the Ethernet technology developed by Dr.
Metcalfe as its official standard (802.3). This
standard remains the basic technology used in
an effective data transfer system that continues
to be developed (Fast Ethernet, 10-Gigabit
Ethernet, switching, full duplex data transfer,
wireless LAN).
One Standard, Many Protocols.
Generally speaking, Ethernet is also suitable
for automation applications. Nevertheless, the
requirements of industrial communication are
more rigorous with regard to the mechanical
and electrical characteristics of the devices and
media used.
Two examples that can be named here are
ambient conditions and real-time behavior.
In addition, no uniform application protocol
exists that is tailored to meet the needs of
automation technology. A host of different
organizations have defined higher application
protocols that can be embedded in the standard
Ethernet data package. As a result, different
protocols and specifications are currently in use.
Neither protocols are compatible with
one another:
TCP/IP (“Office” Ethernet Protocol)
EtherNet/IP (ODVA)
PROFINET (Profibus user organization)
Modbus/TCP (Modbus-IDA Group)
In addition, other manufacturer-specific
approaches exist such as EtherCat, Ethernet-
Powerlink, and JetSync. Lumberg Industrial
Ethernet products have been designed for
use with TCP/IP, EtherNet/IP, PROFINET, and
Modbus/TCP systems.
Data Transfer Technology
While there are different approaches to
real-time communication, all of them have a
common core, which comprise the established
standards of Layers 1-2 as well as the Ethernet
data transfer technology and bus access
procedure (CSMA/CD, Layer 2). All systems
support industrial IT functions such as Web
servers, file transferring, and e-mail. For IT
functions such as these, the Internet protocol
(Layer 3) as well as TCP and UDP protocol (Layer
4) are used. In addition, other IT standards can
be used such as Hypertext Transfer Protocol
(http) and File Transfer Protocol (FTP).
Carrier Sense Multiple Access with
Collision Detection (CSMA/CD)
MA-Multiple Access All devices in an Ethernet
network are equal and can exchange data with
other devices at any time. Devices access media
together. Ethernet does not rely on a master/
slave procedure of the type used with field
busses, where communication is controlled by a
central device.
CS-Carrier Sense
If a device wants to send a data package, it first
checks to see whether the medium is available
or communication is already in progress. If
the medium is busy, the device will wait for
completion of the current data transfer and will
only send data when the medium is no
longer busy.
CD-Collision Detection
While sending data, the device monitors the
medium to detect collisions with data packages
sent by other devices. If a collision has been
detected, the devices involved stop sending
data and wait for a specific amount of time to
elapse before restarting the sending procedure.
The system assumes that a data package has
been sent successfully if no collisions occur.
In this process, the transfer time depends
greatly on the power supply load and cannot
be predetermined. For this reason, this data
transfer procedure is only suitable for certain
types of industrial automation.
The performance of an Ethernet network can
be improved through the use of switches and
Ethernet interfaces with full duplex operation.
The CSMA/CD procedure is deactivated during
full duplex device operation (simultaneous data
package sending and receiving).
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